使用Comparable接口的小例子

public class Student implements Comparable<Student> {

private int id;

private String name;

private int age;

public Student(int id, String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}

@Override
public int compareTo(Student o) {
if (id > o.id) {
return 1;
} else if (id < o.id) {
return -1;
}
return 0;
}

@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("学生的编号：" + id + ", ");
sb.append("学生的姓名：" + name + ", ");
sb.append("学生的年龄：" + age);
return sb.toString();
}
}

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Test {
public static void main(String[] args) {
List<Student> list = new ArrayList<Student>();
list.add(new Student(3, "ZhangSan", 21));
list.add(new Student(2, "LiSi", 22));
list.add(new Student(1, "WangWu", 23));

System.out.println("排序前：");
for (Student stu : list) {
System.out.println(stu);
}

System.out.println("排序后：");
Collections.sort(list); // 执行自动排序
for (Student stu : list) {
System.out.println(stu);
}
}
}